1. Field of the Invention
The present invention relates to an electrical connector assembly, and particularly to an assembly having a board hold down for detachably holding a circuit board to another circuit board thereof.
2. Description of Related Art
Card edge connectors, such as PCI and PCI Express connectors, are widely used to connect daughter cards and mother boards. Typically, each of the card edge connectors generally comprises an elongate housing defining an elongate slot for receiving a mating edge of the daughter card, a plurality of terminals are spaced along one or both sides of the slot for engaging conductive pads disposed on the mating edge of the daughter card, and a pair of latch members attached to opposite ends of the housing. For example, U.S. Pat. No. 5,484,302 (the '302 patent) shows such a card edge connector.
The card edge connector of the '302 patent is arranged to be mounted on a mother board and to finally hold a daughter card, which is inserted at an angle relative to the housing, in an orientation which is parallel to the mother board. The card edge connector has discrete metal latches held in guide frames which extend outwardly from opposite ends of a housing. A plurality of terminals are received in the housing and have solder tails which are electrically connected to the mother board by surface mount soldering. The latches have integral solder tabs which are also attached to the mother board by surface mounting soldering to increase the retention of the card edge connector to the mother board and to reduce stresses imposed on the solder connections of the terminals. The solder tails of the terminals and the solder tabs of the latches must be coplanar so that good solder joints can be produced, but it is difficult to ensure a close coplanarity tolerance on these parts. Also, the latches should extend precisely perpendicular to the housing for effective latching of the daughter card and for proper alignment with solder pads on the mother board. There is a need for the card edge connector with improved control for positioning of the latches. Further, the guide frames increase a longitudinal dimension of the housing, so a large space of the mother board is needed to accommodate the card edge connector. This problem is sometimes undesired where several card edge connectors are arranged on the mother board side by side. The similar card edge connectors having the integrally formed latches thereof, are also shown in U.S. Pat. Nos. 5,997,332 and 6, 663,407.
Hence, an electrical connector assembly having an improved board hold down to solve the above problems is desired. It is noted that U.S. Pat. No. 4,712,939 discloses a separate fixation member 17 mounted on the plate to retain the rear edge section of a printed circuit board, of which the front edge section is inserted into the substrate support 15, in a parallel manner. U.S. Pat. No. 5,281,149 further discloses an upper circuit board being spatially retained above the lower circuit board in a parallel manner by a discrete board locking member (14/45). Thus, based upon the aforementioned patents, it is naturally desired to change the latch structure, which is integrally located on the housing of the card edge connector, to a separate latch device which is independently/discretely mounted on the mother board instead of mounting to the housing of the card edge connector. The invention further defines a specific type latch structure for compliance with the mother board structure, the daughter board structure and the moving path of the inserted daughter board.